viirya commented on code in PR #36809:
URL: https://github.com/apache/spark/pull/36809#discussion_r898652235
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala:
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@@ -4345,32 +4340,42 @@ object ApplyCharTypePadding extends Rule[LogicalPlan] {
}
/**
- * Removes all [[TempResolvedColumn]]s in the query plan. This is the last
resort, in case some
- * rules in the main resolution batch miss to remove [[TempResolvedColumn]]s.
We should run this
- * rule right after the main resolution batch.
+ * The rule `ResolveAggregationFunctions` in the main resolution batch creates
+ * [[TempResolvedColumn]] in filter conditions and sort expressions to hold
the temporarily resolved
+ * column with `agg.child`. When filter conditions or sort expressions are
resolved,
+ * `ResolveAggregationFunctions` will replace [[TempResolvedColumn]], to
[[AttributeReference]] if
+ * it's inside aggregate functions or group expressions, or to
[[UnresolvedAttribute]] otherwise,
+ * hoping other rules can resolve it.
+ *
+ * This rule runs after the main resolution batch, and can still hit
[[TempResolvedColumn]] if
+ * filter conditions or sort expressions are not resolved. When this happens,
there is no point to
+ * turn [[TempResolvedColumn]] to [[UnresolvedAttribute]], as we can't resolve
the column
+ * differently, and query will fail. This rule strips all
[[TempResolvedColumn]]s in Filter/Sort and
+ * turns them to `AttributeReference` so that the error message can tell users
why the filter
Review Comment:
nit:
```suggestion
* turns them to [[AttributeReference]] so that the error message can tell
users why the filter
```
To be consistent in the whole comment.
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